Process for the extrusion of plastics tending to adherence

Abstract

A process for the extrusion of plastics, such as plastics that tend to adhere or stick to parts of an extruder, using a planetary roller extruder in the feed part.

What is claimed is: 
     
       1. A material extruder, comprising:
 a housing comprising an internal toothing formed by a plurality of housing teeth which extend along an axial extension of the housing, each housing tooth of the internal toothing extending radially from a root at a root circle inwardly to a top; 
 a central spindle disposed within said housing; 
 planetary spindles configured and disposed to rotate about said central spindle between said central spindle and said housing; 
 each of said planetary spindles comprising an external toothing configured to mesh with said internal toothing of said housing; 
 said housing comprising an inlet opening configured to permit feeding of material to be extruded into an interior of said housing; and 
 a feed guide being disposed at said inlet opening to guide material to be extruded into said inlet opening, 
 wherein at least one housing tooth extends axially along a regular height portion and a shortened height portion, and 
 wherein a regular height of the at least one housing tooth, defined by a radial distance from the root circle to the top of the at least one housing tooth at the regular height portion, is greater than a shortened height of the least one housing tooth, defined by a radial distance from the root circle to the top of the at least one housing tooth at the shortened height portion. 
 
     
     
       2. The material extruder according to  claim 1 , wherein a plurality of shortened housing teeth each have a shortened height portion and a regular height portion, the plurality of shortened housing teeth including housing teeth which are disposed within a circumferential distance from said inlet opening along an interior circumference of said housing in a direction of rotation of said central spindle. 
     
     
       3. The material extruder according to  claim 2 , wherein the circumferential distance within which said plurality of shortened housing teeth extends along the interior of said housing in the direction of rotation of said central spindle is one of (C), (D), (E), and (F):
 (C) at least 10% of the interior circumference of said housing; 
 (D) at least 20% of the interior circumference of said housing; 
 (E) at least 50% of the interior circumference of said housing; and 
 (F) at least 75% of the interior circumference of said housing. 
 
     
     
       4. The material extruder according to  claim 1 , wherein one of (A) and (B):
 (A) the shortened height is at most 10% of the regular height; and 
 (B) the shortened height is at most 20% of the regular height. 
 
     
     
       5. The material extruder according to  claim 1 , wherein an axial extension of the shortened height portion is one of (G), (H), and (I):
 (G) in a range of 30% less to 30% greater than a width of said inlet opening; 
 (H) in a range of 20% less to 20% greater than a width of said inlet opening; and 
 (I) in a range of 10% less to 10% greater than a width of said inlet opening. 
 
     
     
       6. The material extruder according to  claim 1 , wherein flanks or sides of the at least one housing tooth have a lesser inclination along its shortened height portion, when viewed in cross section, than along its regular height portion. 
     
     
       7. The material extruder according to  claim 1 , wherein:
 the at least one housing tooth has a rounded top at the shortened height portion having a radius of curvature, when viewed in cross section, that is one of (J) and (K): 
 (J) at least 25% of a height of the at least one housing tooth; and 
 (K) at least 50% of a height of the least one housing tooth. 
 
     
     
       8. The material extruder according to  claim 1 , wherein said housing comprises heating and cooling channels disposed inside said housing. 
     
     
       9. The material extruder according to  claim 8 , wherein:
 said heating and cooling channels have a diameter that is less than or equal to half the diameter of a pitch circle of said internal toothing. 
 
     
     
       10. The material extruder according to  claim 1 , wherein each of said planetary spindles comprises a transport spindle or a transport spindle section having fewer planetary spindle teeth and/or greater space between adjacent planetary spindle teeth than another section of each of said planetary spindles and/or an additional set of planetary spindles in said material extruder. 
     
     
       11. The material extruder according to  claim 10 , wherein each of said transport spindles or said transport spindle sections comprises at least one fewer planetary spindle teeth than another section of each of said planetary spindles and/or said additional set of planetary spindles. 
     
     
       12. The material extruder according to  claim 10 , wherein each of said transport spindles or said transport spindle sections comprises one of (O), (P), (Q), and (R):
 (O) four planetary spindle teeth; 
 (P) three planetary spindle teeth; 
 (Q) two planetary spindle teeth; and 
 (R) one planetary spindle tooth. 
 
     
     
       13. The material extruder according to  claim 12 , wherein one of (S) and (T):
 (S) said transport spindles or said transport spindle sections comprise an even number of planetary spindle teeth; and
 each of said internal toothing and said central spindle comprise an odd number of teeth; and 
 
 (T) said transport spindles or said transport spindle sections comprise an odd number of planetary spindle teeth; and
 each of said internal toothing and said central spindle comprise an even number of teeth. 
 
 
     
     
       14. The material extruder according to  claim 13 , wherein each of said planetary spindles comprises said transport spindle section and another planetary spindle section which comprises a different type of toothing. 
     
     
       15. The material extruder according to  claim 14 , wherein said different type of toothing comprises teeth that are spaced apart at a different distance than said teeth of said transport spindle section, and/or have a different shape or cross-sectional profile. 
     
     
       16. The material extruder according to  claim 15 , wherein said transport spindle section extends over one of (U), (V), and (W):
 (U) at least 50% of the length of each of said planetary spindles; 
 (V) at least 70% of the length of each of said planetary spindles; and 
 (W) at least 90% of the length of each of said planetary spindles. 
 
     
     
       17. The material extruder according to  claim 16 , wherein each of said planetary spindles is spaced apart from one another at the same interval. 
     
     
       18. The material extruder according to  claim 17 , wherein each of said transport spindle sections is configured such that at least one planetary tooth meshes with each space between the teeth of said internal toothing and with each space between the teeth of said central spindle, which meshing with each space occurs within one of (aa), (bb), (cc), and (dd):
 (aa) ten rotations of the planetary spindles around the central spindle; 
 (bb) seven rotations of the planetary spindles around the central spindle; 
 (cc) four rotations of the planetary spindles around the central spindle; and 
 (dd) one rotation of the planetary spindles around the central spindle. 
 
     
     
       19. The material extruder according to  claim 1 , comprising a plurality of shortened housing teeth, each having a shortened height portion and a regular height portion, the shortened height portions being arranged downstream of the inlet opening. 
     
     
       20. The material extruder according to  claim 19 , wherein the internal toothing comprises a plurality of housing teeth, at least 10% of which have a shortened height portion. 
     
     
       21. The material extruder according to  claim 19 , wherein the shortened housing teeth each have a shortened height along their shortened height portions, and wherein the shortened heights of the shortened housing teeth which are circumferentially further from the inlet opening exceed the shortened heights of the shortened housing teeth which are circumferentially closer to the inlet opening. 
     
     
       22. The material extruder according to  claim 1 , wherein the shortened height portion of the at least one housing tooth is axially aligned with the inlet opening. 
     
     
       23. The material extruder according to  claim 1 , wherein an axial extension of the shortened height portion is at most 90% of a width of the inlet opening.